Separation of mica from clay by froth flotation of clay

ABSTRACT

Mica, present as an impurity in kaolin clay, is removed from the clay particles by stage-wise froth flotation of the clay in a dispersed alkaline pulp, using as a collector for the clay a complex phosphate ester of a nonionic surfactant of the ethylene oxide-adduct type.

United States Patent [1 Yang [ 51 Sept. 24, 1974 1 1 SEPARATION OF MICA FROM CLAY BY FROTH FLOTATION 0F CLAY [75] Inventor: David C. Yang, Edison, NJ.

[73] Assignee: Engelhard Minerals & Chemicals Corporation, Township of Woodbridge, NJ.

[22'] Filed: Aug. 1, 1972 [21] App]. No.2 277,134

[52] US. Cl. 209/167 [51] Int. Cl B03d 1/06 [58] Field of Search 209/160, 167, 5

[.56] References Cited UNITED STATES PATENTS 2,162,494 6/1939 Trotter 209/166 2,249,570 7/1941 Lane 209/166 2,303,962 12/1942 Tantaron 209/166 2,759,962 8/1956 Zenftntan 209/166 [Pi 2,857,051 10/1958 Noblitt ..209/167 3,037,627 6/1962 Nazen 209/167 X 3,259,237 7/1966 Schueld 209/166 X 3,278,028 10/1966 Millsups 209/160 3,329,265 7/1967 Browning 209/166 3,462,013 8/1969 Mercade 209/166 X 3,480,143 11/1969 Mitzmagel 209/166 3,567,636 3/1971 Katzenstein 252/325 FOREIGN PATENTS OR APPLICATIONS 1,044,733 11/1958 Germany 209/166 Primary Examiner-Robert Halper Attorney, Agent, or Firm-Melvin C. Flint; Inez L. Moselle [5 7 ABSTRACT Mica, present as an impurity in kaolin clay, is removed from the clay particles by stage-wise froth flotation of the clay in a dispersed alkaline pulp, using as a collector for the clay a complex phosphate ester of a nonionic surfactant of the ethylene oxide-adduct type.

3 Claims, No Drawings SEPARATION OF MICA FROM CLAY BY FROTH FLOTATION OF CLAY BACKGROUND OF THE INVENTION High purity kaolin clay is widely used as a coating pigment for paper and paints. Such pigments must be free from undesired impurities, of which mica is an example. The presence of mica in more than trace quantity may render the clay unsatisfactory for use as a pigment.

Mica can be removed from clay with reasonable ease by gravimetric means or flotation when the clay is coarse. However, when the clay particles and micaceous impurities are fine, the separation is very difficult. Froth flotation with conventional ionic collectors is usually unsuccessful because mica and kaolin, both silicate minerals, have remarkably similar flotation properties.

THE INVENTION An object of the invention is to provide a novel method for floating finely divided kaolin clay from a micaceous impurity.

A specific object is to provide a novel flotation method for floating kaolin clay from mica.

Briefly stated, in accordance with the present invention, a micaceous impurity, especially muscovite mica, is removed from kaolin clay by deflocculating a pulp of the impure clay and subjecting the deflocculated ore pulp to stage-wise froth flotation in an alkaline flotation circuit in the presence of a complex phosphate ester, or a salt thereof, of a nonionic surface active ethylene or propylene oxide adduct, producing a froth which is a concentrate of purified clay and a tailings which is a concentrate of mica. No activator for mica (e.g., an aluminum salt) is used. When an aluminum salt is employed in conjunction with the complex phosphate ester, as disclosed and claimed in my copending application, Ser. No. 266,159, filed June 26, 1972, the froth product will be a concentrate of mica.

PRIOR ART Various combinations of anionic and cationic reagents have been suggested as flotation collectors for micaceous minerals. Reference is made to the follow- DETAILED DESCRIPTION In putting the invention into practice, the impure clay is initially blunged in water and coarse grit and undispersible agglomerates are removed in conventional manner, e. g., by sedimentation or screening. Preferably soda ash, in amount sufficient to adjust pH to a value within the range of 8 to 11 and partially disperse the clay, is added before degritting.

The degritted pulp of impure clay should be welldeflocculated before flotation is carried out. The dispersant (deflocculating agent) used may vary with the nature of the clay. In some'cases soda ash, added before or after degritting, will suffice to provide a welldeflocculated pulp suitable for flotation. In most cases,

however, a more powerful dispersant will be required. The most satisfactory dispersant may vary with the nature of the clay. In many cases, sodium lignosulfonate will give best results. Other strong clay dispersants include sodium silicate and sodium condensed phosphates.

The phosphate esters of nonionic surface active agents which are used as collectors in carrying out the invention are described in U.S. Pat. No. 3,567,636 to Katzenstein. The pertinent disclosures in the Katzenstein patent as to the composition of such esters and to their preparation are incorporated herein be reference. Briefly, these are complex phosphate esters (or salt thereof) of a nonionic surface active compound, the phosphate being selected from the group consisting of monoesters, diesters and mixtures thereof, the nonionic surface active compound being the condensation product of an organic hydroxy compound of from eight to 50 carbon atoms selected from the group consisting of alkyl phenol and alkanols with at least 1 mole of an alkylene oxide having from two to three carbon atoms, the nonionic surface active compound containing a maximum of about 50 percent by weight of alkylene oxide based on the weight of the nonionic surface active compound.

The phosphate esters are commercially available under the trade name GAFAC and are anionic surfactants. The commerical products are usually mixtures of monoand di-esters. The product GAFAC RM 510 is understood to be a mixture of monoester and diester, principally diester. The monoester constituent may be described by the formula:

R O (CHiCHa 0% O aoaimomok 0 aowmcmfl OH wherein'R alkylaryl and n is 5 to 7.

Obviously the ester can be used in salt form (e.g., so-

dium, ammonium, calcium, magnesium). In use the acid would be converted to alkali metal salt fonn in the basic clay pulp.

An essential feature of the method of the invention resides in the stage-wise addition of the phosphate ester collector. Total amount of ester collector generally is within the range of 1.5 to 5.0 lb./ton, usually 2.0 to 3.0 lb./ton. Normally, no more than 1.0 lb./ton is added during any stage. A typical amount to add during each stage is within the range of about 0.1 to 1.0, preferably 0.2 to 0.8 lb./ton.

The phosphate esters normally will not provide adequate frothing when added stage-wise in small amount. Thus, a small amount of a conventional frother such as methyl isobutyl carbinol or pine oil is normally added to develop adequate froth.

All of the frother may be added during the first stage or additional frother may be required in one or more subsequent stages.

During the first stage, the deflocculated pulp is conditioned with phosphate ester, preferably using prolonged conditioning, followed by frothing and froth removal. The flotation tailings are then conditioned with additional phosphate ester, again followed by frothing and froth removal. This is repeated one or more additional times.

Flotation may be carried out at solids within the range of about percent to 50 percent, preferably 20 percent to 45 percent solids.

After flotation the clay in the froth product may be redispersed, fractionated in conventional manner to recover one or more fine size fractions of beneficiated clay. In many cases, the fine fractions will be lower in residual mica than the coarse fraction of the flotation purified clay.

The following example is given for illustrative purposes and is not to be considered as limiting upon the invention.

The clay used in the test was an impure kaolin from France. The principal impurity in the clay was muscovite. The degritted minus 325 mesh (Tyler) portion of the impure clay analyzed 1.97 percent K 0, corresponding to 16.7 percent muscovite.

A sample of the crude clay (9,000 gm., dry basis) was blunged in deionized water at 30 percent solids for minutes. Soda ash was then added in amount of 2.0 lb./ton, the pH was adjusted to 9.0 using caustic soda, and the slip was conditioned for 15 minutes. The slip was screened on a'Sweco vibratory screen and the minus 325 mesh fraction of the slip was recovered. A portion of the minus 325 mesh slip was fractionated with a minus 5 micron cutoff and the minus 5 micron fraction was analyzed for K 0 content for purposes of comparison.

The degritted slip (minus 325 mesh fraction) was charged to a Fagergren conditioner. Sodium lignin sulfonate was added in amount of 1.75 lb./ton, followed by conditioning for 6 minutes.

GAFAC MO-510, 0.5 lb./ton, was incorporated, followed by 16 minutes conditioning. The pulp was then conditioned for 1 minute with a drop of methyl isobutyl carbionol. pH was 9.0.

The pulp was transferred to a Denver flotation machine and froth was collected for 10 minutes. After removing froth from the first stage of flotation, an additional 0.5 lb./t0n of GAFAC was added, followed by 2 minutes conditioning and reflotation (second stage) for 10 minutes without further addition of frother. This was repeated a total of four times (total collector used was 2.0 lb./ton GAFAC MO-510).

The combined froths (FP l-4) were combined and a portion was analyzed for K 0 to estimate mica content of the purified clay. FP l-4 was then redispersed and fractionated at 5 microns. The minus 5 micron cut was analyzed for K 0. In similar manner the tailings product was analyzed for K 0 before and after fractionation to minus 5 microns. The results are summarized in table form along with K 0 analyses and estimated mica contents of the impure clay before and after fractionation. V H I Metallurgical results in the table show that stage-wise froth flotation using a phosphate ester complex as the collector for kaolin reduced the K 0 content of the minus 5 micron fraction of the clay from 1.53 percent, corresponding to 13.0 percent mica, to 1.14 percent K 0, corresponding to 9.66 percent mica. Thus, about one-third of the mica was removed. Overall clay recovery was 41.4 percent, with an 18.9 percent recovery of a minus 5 micron fraction.

I claim:

1. In a process for removing a micaceous impurity from kaolin clay, the steps comprising dispersing an aqueous pulp containing kaolin clay and micaceous impurity with sodium lignosulfonate, conditioning the pulp with a complex phosphate ester, or salt thereof, of a nonionic alkylene oxide adduct as a collector for the kaolin clay, the pulp being free from an activator for the micaceous impurity, and subjecting the pulp to froth flotation at a pH in the range of 9 to 1 l, producing a froth which is a concentrate of purified clay and a tailings enriched in micaceous impurity, said phosphate ester collector being a nonionic surface active agent which is selected from the group consisting of monoester, diester and mixtures thereof, said nonionic alkylene oxide adduct being the condensation product of an organic hydroxy compound which contains from 8 to 50 carbon atoms and is selected from the group consisting of alkyl phenol and alkanols with at least 1 mole of an alkylene oxide containing from two to three carbon atoms, said nonionic alkylene oxide adduct containing a maximum of about 50 percent by weight of alkylene oxide.

2. The process of claim 1 wherein said tailings is reconditioned with additional phosphate ester collector and subjected to froth flotation at least one more time, and combining the froth products to produce a purified clay product.

3. The process of claim 2 in which said phosphate ester is a mixture of monoester and diester, principally diester, wherein the monoester has the following formula: 

2. The process of claim 1 wherein said tailings is reconditioned with additional phosphate ester collector and subjected to froth flotation at least one more time, and combining the froth products to produce a purified clay product.
 3. The process of claim 2 in which said phosphate ester is a mixture of monoester and diester, principally diester, wherein the monoester has the following formula: 